1. Field of the Invention
The present invention relates to a wiper control apparatus for controlling the movement of a wiper blade of a wiper mounted on a motor vehicle and used to remove waterdrops sticking to the surface of its windshield.
2. Prior Art
FIG. 1 is a circuit diagram of a conventional wiper, wherein the wiper comprises a battery 10, an ignition switch 20, a wiper switch 30 and a wiper driving means 40.
The wiper switch 30 is set to an OFF position, a first closed position LO or a second closed position HI. In the OFF position, a stop terminal S and a first output terminal +1 are connected and, in the closed position LO, the first output terminal +1 and a battery terminal B are connected and, further in the closed position HI, a second output terminal +2 and the battery terminal B are connected.
The wiper driving means 40 has a wiper motor 41 and a cam switch 42. Of the aforesaid two components, the wiper motor 41 actuates the wiper on receiving power from the output terminals +1, +2 of the wiper switch 30 through lines l.sub.1, l.sub.2, whereas the cam switch 42 has a moving contact 42c connected to the stop terminal S through a voltage terminal 42a, a ground termrinal 42b and a line l.sub.4. The moving contact 42c is switched to the ground terminal 42b while the wiper blade stays in the predetermined lower position of the windshield (outside the driver's ken) and to the voltage terminal 42a while the wiper blade stays in a position other than the aforesaid one.
On the other hand, the power is supplied from the battery 10 to the voltage terminal 42a through lines l.sub.7, l.sub.6, l.sub.5 and simultaneously to the battery terminal B through the lines l.sub.7, l.sub.6, l.sub.3 when the ignition switch 20 is closed.
Subsequently, the operation of the conventional wiper in several cases will be described as follows:
(i) The wiper switch 30 is off while the ignition switch 20 is closed. PA0 (ii) The wiper switch 30 is in the first closed position LO while the ignition switch 20 is closed. PA0 (iii) The wiper switch 30 is in the second closed position HI while the ignition switch 20 is closed. PA0 (iv) The wiper switch 30 is switched from the closed position HI to LO to off while the ignition switch 20 is closed.
In this case, the wiper motor 41 is not driven and the wiper blade is also unoperated because the line l.sub.3 is cut off the lines l.sub.1, l.sub.2.
In this case, the current flows in the following order: battery 10.fwdarw.line l.sub.7 .fwdarw.ignition switch 20.fwdarw.lines l.sub.6, l.sub.3 .fwdarw.battery terminal B.fwdarw.output terminal +1.fwdarw.line l.sub.1 .fwdarw.wiper motor 41.fwdarw.ground. The wiper motor 41 driven thereby causes the wiper blade to clean the windshield.
In this case, the current flows in the following order: battery 10.fwdarw.line l.sub.7 .fwdarw.ignition switch 20.fwdarw.lines l.sub.6, l.sub.3 .fwdarw.battery terminal B.fwdarw.output terminal +2.fwdarw.line l.sub.2 .fwdarw.wiper motor 41.fwdarw.ground. The wiper motor 41 driven thereby causes the wiper blade to clean the windshield. Moreover, because the output current of the output terminal +2 is higher than that of the output terminal +1, the number of revolutions of the wiper motor 41 is greater than that in the case of the first closed position LO and consequently the wiper blade moves faster.
In this case, the output terminal +1 and the stop terminal are connected when the wiper switch 30 is switched from the closed position HI or LO to off. In case the wiper blade is in the midposition of the windshield, the moving contact 42c in contact with the voltage terminal 42a thereby causes the current to flow in the following order: battery 10.fwdarw.line l.sub.7 .fwdarw.ignition switch 20.fwdarw.lines l.sub.6, l.sub.5 .fwdarw.voltage terminal 42a.fwdarw.moving contact 42c.fwdarw.line l.sub.4 .fwdarw.stop terminal S.fwdarw.output terminal +1.fwdarw.line l.sub.1 .fwdarw.wiper motor 41.fwdarw.ground. In consequence, the wiper motor 41 is kept driven even though the wiper switch is opened so as to move the wiper blade. When the wiper blade is moved up to the predetermined lower position of the windshield, the moving contact 42c contacts the ground terminal 42b and causes the wiper blade to stop as the supply of power to the wiper motor 41 is cut off. Consequently, the wiper blade is moved up to the predetermined lower position of the windshield and stopped without being stopped in the midposition. The wiper blade is thus caused to stop without impeding the driver's ken.
Notwithstanding, the prior art poses the following problems: If the ignition switch 20 is switched from the closed to open position while the wiper switch 30 is held is the closed position HI or LO, the wiper motor 41 is caused to stop simultaneously with the aforesaid switching operation and the wiper blade is stopped thereby. For this reason, if the ignition switch 20 is opened while the wiper blade is in the midposition of the windshield, the wiper blade is stopped in the inconvenient mid-position of the windshield. To remedy the disadvantage in that the wiper blade is stopped in the midposition, it requires extremely troublesome operation. More specifically, it requires to close the igntition switch 20 again and the open the wiper switch 30 so as to confirm that the wiper blade has stopped in the predetermined lower position of the windshield before opening the ignition switch 20.
There is another conventionally used wiper comprising a wiper control switch for producing a signal designating the wiper blade operational mode, an intermittent wiper relay for letting the wiper blade intermittently operate for a predetermined time by operating on receiving the signal specifying the intermittent operation of the wiper blade from the wiper control switch, a wiper motor for driving the wiper blade in response to the signals received from the wiper control switch and the intermittent wiper relay, and wire harness for connecting the aforesaid parts. This wiper makes possible the intermittent operation of its wiper blade because of the operation of the intermittent wiper relay as a circuit, variable intermittent time operation and mist operation wherein the wiper blade is operated once. In such a conventional wiper, the signal directly applied from the wiper control switch to the wiper motor is used to provide low and high speed cleaning operation. In every type of the aforesaid operation, the wiper motor is designed to stop the wiper blade after it has returned to the predetermined stop position when the wiper control switch is turned off.
FIG. 2 shows an example of the construction of a conventional wiper control apparatus.
In FIG. 2, the wiper control apparatus shown therein comprises a wiper motor 1 for driving a wiper blade (not shown) for removing waterdrops attaching to the windshield and the like of an automobile and giving favorable ken to the driver, an intermittent wiper relay for controlling the operation of the wiper motor 1 and letting the wiper blade perform intermittent and mist operation, a wiper control switch for producing a control signal for specifying the operational mode of the wiper blade and controlling not only the intermittent but also high and low speed operation in addition to interrupting opeation, and a washer motor 4 for sending a jet of rinsing water to the windshield.
The wiper controlling apparatus employs voltage +B supplied by a power supply 6 through an ignition switch 5 as operational power supply voltage.
The ignition switch 5 includes a switch SW1 for supplying the power supply voltage +B to systems other than the engine system and a switch SW2 for supplying the power supply voltage +B to the engine system when the switch 2 conducts so as to make the engine operable. The operational power supply voltage is supplied to the wiper control apparatus through the switch SW1.
The wiper motor 1 is equipped with a wiper motor 11 for operating the wiper blade at high or low speed and a limit switch 12 for detecting whether or not the wiper blade has returned to (or stopped at) the predetermined reset position. The motor 11 is designed to revolve at high speed when the power supply voltage +B is given to the input terminal H and at low speed when the power supply voltage +B is supplied to the input terminal L. The limit switch 12 operates in such a manner as to connect the S terminal to a ground terminal E when the wiper blade returns to the reset position and, while the wiper blade remains in the midposition of the windshield, connect the terminal S to the terminal B supplied with the power supply voltage +B. Accordingly, the position of the wiper blade is detectable.
The intermittent wiper relay 2 is equipped with a terminal a connected to the terminal S of the wiper control switch 3, a terminal b connected to the terminal S of the limit switch 12, a terminal c for receiving the power supply voltage +B, a terminal d connected to the ground potential of the wiper system through the terminal W of the wiper control switch 3, a terminal f connected to the terminal I of the wiper control switch 3, and a terminal e connected to the ground potential. The intermittent wiper relay 2 is activated when its terminal f is given an activating signal and makes the wiper blade intermittently operate through the wiper motor 1. The control of such intermittent operation is implemented under the control of its internal circuit (not shown). While the wiper relay 2 is unoperative (when the inactive signal is given to the terminal f), the terminals a, b are kept in conduction.
The wiper control switch 3 includes an OFF switch for generating a signal instructing the wiper blade to stop operating, an INT switch for producing a signal instructing the wiper blade to operate intermittently, a HI switch for causing the wiper blade to operate at high speed, and a LOW switch for letting the wiper blade to operate at low speed.
The OFF switch is so arranged as to connect the terminals L, S of the wiper motor 1 through the intermittent wiper relay 2 and stop the operation of the wiper blade. The INT switch is employed to connect the terminals L, S of the wiper motor 1 through the intermittent wiper relay 2 and, by grounding the terminal f of the intermittent wiper relay 2 through the terminal I, given intermittent operation. The LOW switch supplies the power supply voltage +B to the terminal L of the motor 11 of the wiper motor 1 and causes the motor 11 to operate at low speed, whereas the HI switch supplies the voltage +B to the terminal H of the motor 11 and causes the motor 11 to operate at high speed.
In the washer motor 4, the terminal B is supplied with the power supply voltage +B through the switch SW1 of the ignition switch 5, whereas the ground terminal W is grounded at all times through the wiper control switch 3. Accordingly, the washer motor 4 is actuated whenever the switch SW1 of the ignition switch 5 is conducted and usable to supply rinsing liquid to the windshield. Subsequently, the operation will be described.
By keeping the switch SW1 at the first stage of the ignition switch 5 in conduction, the operational power supply voltage +B is supplied from the wiper control system, whereby the wiper control circuit is made operable. On receiving the power supply voltage +B through the switch SW1, the washer motor 4 rotates and makes possible the supply of the rinsing liquid. Any operational instruction to be given to the wiper blade is given by conducting any one of the operational instructing switches of the wiper control switch 3. More specifically, the Hi switch of the wiper control switch is energized to operate the wiper blade at high speed while the power supply voltage +B is supplied to the terminal H of the motor 11. When the wiper blade is operated at low speed, the LOW switch is conducted and the power supply voltage +B is supplied to the terminal L of the motor 11. The motor is thus rotated at high or low speed and the wiper blade is consequently moved at high or low speed.
In order to operate the wiper blade intermittently, it can be attained by conducting the INT switch, placing the terminal f of the wiper relay 2 to the ground potential and making the intermittent wiper relay 2 active. The terminal L of the motor 11 and the terminal S of the limit switch 12 are connected to the terminals a, b of the intermittent wiper relay 2, respectively. The limit switch 12 is used to make the terminal S equal to the ground potential through the terminal E when the wiper blade is restored to the reset position and to connect the terminal S to the power supply voltage +B through the terminal B when the wiper blade is in the midposition. The intermittent wiper relay 2 responds when the intermittent operation instructing signal is given to the terminal f and controls the operation of the motor 11 by giving the power supply voltage +B from the terminal a to the terminal L of the motor 11 through the wiper control switch 3. In other words, when the intermittent operation instructing signal is given to the wiper control switch 3, the switch causes its terminal a to produce the voltage +B for a predetermined period of time and the motor 11 to rotate at low speed through the control switch 3, so that the wiper blade is operated. When the wiper blade is returned to the reset position upon the completion of the first operation of the wiper blade, the terminal S of the limit switch 12 is connected to the terminal E so that the ground potential is established in the terminal S. When the ground potential is established in the terminal S, the terminal b of the intermittent wiper relay 2 is at the ground potential. The intermittent wiper relay 2 responds to the ground potential of the terminal b and causes the terminal a to be at the groupnd potential and also the terminal L of the motor 11 to be at the ground potential through the wiper control switch 3. Further the intermittent wiper relay 2 stops the motor 11 from turning and thus stops the wiper blade from operating. After the passage of a predetermined time, the intermittent wiper relay makes the terminal a supply the power supply voltage +B from the terminal a again to turn the motor 11, so that the aforesaid operation is repeated. As the power supply voltage +B supplied from the terminal a, the voltage +B given to the terminal c is employed. The control of the intermittent operation is performed by a control circuit (not shown) included in the intermittent wiper relay 2.
When the OFF switch of the wiper control switch 3 is conducted to stop the operation of the wiper blade, the terminals L, S of the wiper motor 11 are connected through the intermittent wiper relay 2. While the intermittent wiper relay is left unoperative, its terminals a, b are made conductive thereby. Accordingly, when the wiper blade is not in the reset position but in the midposition, the terminal S of the limit switch 12 is kept connected to the terminal B and the motor 11 is allowed to continue to turn. When the wiper blade is returned to the reset position, the terminal S of the limit switch 12 is connected to the terminal E and the terminal L of the motor 11 is set at the ground potential, so that the motor 11 stops turning.
If the wiper control switch 3 is turned off during the intermittent operation of the wiper blade, the terminal f of the intermittent wiper relay 2 is not supplied with the ground potential and, because the terminals a, b are connected, the motor 11 stops turning after the wiper blade is returned to the reset position.
As set forth above, even though the wiper control switch 3 is turned off during the operation of the wiper in the conventional wiper control circuit, the wiper motor 1 is caused to stop operating after the wiper blade is returned to the reset position.
However, since the power supply voltage for operating the wiper control circuit is supplied through the ignition switch 5, the power supply voltage therefor is stopped immediately after the ignition switch 5 is turned off. In consequence, the motor 11 stops to operate when the ignition switch 5 is turned off during the operation of the wiper blade, thus causing no power supply voltage to be supplied to the wiper control circuit. Accordingly, the wiper blade is stopped in the midposition without being returned to the stop (reset) position.
In order to bring the wiper blade to the stop position based on the aforesaid understanding, the following troublesome steps are required: namely, the steps of conducting the switch SW1 in the first stage of the ignition switch 5 again, making the wiper control circuit operational, then turning off the wiper control switch 3 and turning off the switch SW1 of the ignition switch 5 after confirming that the wiper blade has stopped at the reset position.
Assuming that the driver has left the wiper blade in the midposition without noticing that he has forgotten to turn off the wiper control switch 3 and that he has come to notice the aforesaid fast later, the wiper blade may be moved to the reset position immediately when the switch SW1 at the first stage of the ignition switch is turned on and the windshield may be damaged by the dust and the like sticking thereto.